Sensor for detecting leaks in a liquid hydrocarbon dispenser

ABSTRACT

The invention concerns a sensor for detecting leaks in a liquid hydrocarbon dispenser, said sensor comprising a sealed plate arranged at the dispenser base and provided with a collecting container for receiving said liquid hydrocarbons collected by said sealed plate and coming from leaks in the dispenser, said collecting container comprising a sensor at the level of said hydrocarbons, capable of stopping the operation of the dispenser when the hydrocarbon level sensed reaches a predetermined level (N). The invention is useful for protecting the environment against hydrocarbon pollution.

FIELD OF INVENTION

The present invention relates to a sensor for detecting leaks in adispenser for liquid hydrocarbons.

The invention can be applied to particular advantage in the field ofenvironmental protection against hydrocarbons, especially fuels formotor vehicles.

BACKGROUND OF THE INVENTION

In view of growing concerns to preserve the quality of the environment,it appears essential to fit liquid hydrocarbon dispensers with a sensorfor detecting leaks, regardless of where they originate within thedispenser.

Several detection systems have been proposed for this purpose.

Firstly, it is possible to detect the vapours from liquid hydrocarbonsinside the dispenser. This can be achieved either by means ofbiological, optical or combined sensors or by measuring the density ofvapours contained in the dispenser. However, in view of the very markedvariety of temperatures, humidity and quality of installation at servicestations, this type of detection triggers numerous false alarms or, evenworse, no alarm at all. Biological sensors, furthermore, have a tendencyto become poisoned by additives. When it comes to liquid hydrocarbons ofthe gas oil type, these generate no or little vapour and it is difficultto detect their presence other than by the odours of the additives whichthey contain.

It would be conceivable to detect leaks by taking pressure measurementsat different points in the pipework system for the hydrocarbons.However, to detect slight leaks, it is necessary to have a perfectknowledge and model of the distribution of pressure in the passagesdepending on the conditions under which the dispensers are installed onsite and the sensors need to be extremely sensitive, in order of severalmbars, and be capable of withstanding pressure surges of more than 15bars, which require extremely expensive equipment. Moreover, thesoftware must exhibit a high degree of intelligence to be able toprocess data from the sensors. Finally, sensors operating in hazardousareas also need to be security-protected and are therefore veryexpensive.

SUMMARY OF THE INVENTION

Accordingly, the technical problem to be resolved for the purposes ofthe invention is that of proposing a sensor for detecting leaks in aliquid hydrocarbon dispenser that would be simple in design andcost-effective whilst providing perfect efficiency and the requisitesecurity.

This technical problem is resolved for the purposes of the invention dueto the fact that said sensor comprises a sealed plate, arranged on thebase of said dispenser and fitted with a catchment container designed toreceive the liquid hydrocarbons collected by said sealed plate andcoming from leaks in the dispenser, said catchment container having alevel detector for said hydrocarbons, capable of halting operation ofthe dispenser if the detected level of hydrocarbons reaches a givenlevel.

This provides a perfectly reliable sensor due to the presence of thesealed plate in the base of the dispenser where liquid hydrocarbonsemanating from all leaks, regardless of their origin, are collected anddetected. Furthermore, the sensor proposed by the invention usescomponents (plate, catchment container and level detector) which arecheap and easy to install in the dispensers.

By virtue of another advantageous feature of the leakage sensor proposedby the invention, said dispenser has a pump, a flow-rate counter and acomputer, said computer being capable of detecting a flow rate of liquidhydrocarbons in said counter after the dispensing process because saidpump continues to operate for a given period.

As a complement to overall detection of leaks inside the dispenser, thisparticular feature pinpoints any leaks which might occur downstream ofthe flow-rate counter. In practice, after dispensing, immediately afterthe gun is replaced, rather than halting the motor of the pump in thedispenser as usually happens, operation of said motor is continued for aperiod in the order of a few seconds during which the computer continuesto monitor the data from the counter so that if a flow rate is detectedby the computer, it can only be attributable to a leakage downstream ofthe counter, and an indication of this fault can then be given to theservice station manager, pinpointing where the dispenser is faulty. Thisdetection system is particularly useful in the case of dispensers fittedwith double hose vapour recovery devices as a means of detecting anyleaks of liquid hydrocarbons which might be sucked in by the recoverydevice.

The description outlined below with reference to the appended drawings,given by way of illustration and not restrictive in any respect, shouldprovide an understanding of what the invention comprises and how it canbe operated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a liquid hydrocarbon dispenser fitted with aleakage sensor as proposed by the invention.

FIG. 2 is a side view of a level detector of the leakage sensor of FIG.1.

FIG. 3 is a side view of a first variant of the embodiment of the leveldetector illustrated in FIG. 2.

FIG. 4 is a side view of a second variant of the embodiment of the leveldetector illustrated in FIG. 2.

FIG. 5 is a side view of a level detector fitted with a water-leveldetector.

FIG. 6 is a side view of a pipe passage through the sealed plate of FIG.1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a dispenser 1 for liquid hydrocarbons having a pump10 which extracts said hydrocarbons from a storage tank 2 and conveysthem into a gas-release device 20, the purpose thereof being to removethe gases incorporated in the liquid, which is then fed to a flow-ratecounter 30, generally capable of producing a movement in rotation, theangular speed of which is proportional to the hydrocarbon flow-rate. Atransducer 31 of the wheel encoder type enables the mechanical positionof the counter to be converted into electric pulses. Said pulses aretransmitted to a computer 32 in order to establish the volume ofhydrocarbons dispensed and the amount payable on the basis of the unitprice.

Having passed through the flow-rate counter 30, the liquid is conveyedthrough a member 40 providing a connection to a flexible hose 50terminating in a dispenser gun 51.

As may be seen from FIG. 1, the dispenser 1 has a leakage sensor 100essentially comprising a sealed plate 101 arranged on the base of thedispenser 1 and a catchment container 102 designed to receive the liquidhydrocarbons collected by the plate 101 and coming from leaks in thedispenser. In the embodiment illustrated in FIG. 1, the catchmentcontainer 102 is positioned substantially at the centre of the plate101, this latter being of a flared design to facilitate the flow ofhydrocarbons collected to the catchment container 102.

As illustrated in FIG. 1, the catchment container 102 has a leveldetector 103 capable of halting operation of the dispenser 1 if thedetected level of hydrocarbons reaches a given level N. In the examplegiven in FIG. 1, the level sensor 103 is connected to the motor of pump10 of the dispenser, If the given level is reached, the detector 103sends a signal commanding that operation of the motor of the pump 10 behalted.

FIG. 2 illustrates a specific embodiment of the level detector 103 inwhich a float 1031 is placed in the catchment container 102. Theposition of said float 1031 is detected by a position sensor comprisinga magnet 1032 disposed at the non-immersed end of the float 1031 and anelement 1033 sensitive to the magnetic field, such as a Reed relay or aHall effect sensor, and connected to the pump 10. As the catchmentcontainer 102 fills up, the level of the float 1031 rises and themagnetic field detected by the sensitive element 1033 increases until itreaches a high enough value to actuate said sensitive element andtrigger the shutdown of the motor of the pump 10. The level N at whichthe leakage sensor 103 is triggered is calibrated so as to correspond toa given volume of leakage, for example less than 100 cm³.

FIG. 3 illustrates an embodiment of the level detector 103 comprising apiezoelectric transducer 1034 designed to emit an ultrasound wave anddetect the echo reflected from the surface of the liquid hydrocarbons inthe catchment container 102. The time which elapses between emission ofthe ultrasound wave and detection of the echo is directly proportionalto the position of the liquid level in the container 102.

Another embodiment is illustrated in FIG. 4. This is an optical leveldetector comprising an optical fibre 1035 which emits a light wave and areceiving optical fibre 1036, positioned in alignment on either side ofthe catchment container 102. If the level of liquid hydrocarbons hasreached the level N of FIG. 4, the light wave is deflected by reflectionand refraction and the receiving optical fibre 1036 no longer receiveslight radiation and this situation is detected by an optical sensor, notillustrated, located at the end of the optical fibre 1036, which sends asignal to shut down the pump 10.

In view of the fact that water may accidentally get into the catchmentcontainer 102, means must be provided to overcome this problem, which islikely to distort operation of the leakage sensor proposed by theinvention.

A first approach is to make the catchment container 102 so that it canbe moved, enabling the service station manager to purge said recipientof any water each time the dispenser 1 is inspected.

In the case of service stations unattended by personnel, the leveldetector illustrated in FIG. 5 may be used. This latter detector uses apiezoelectric transducer 1034, identical to that of FIG. 3, designed todetect the echoes of the ultrasound wave produced on the one hand at theair/hydrocarbon interface and on the other hand at the hydrocarbon/waterinterface. The time separating these two echoes is directly proportionalto the height h of hydrocarbons.

Clearly, in view of its position in the dispenser 1, the plate 101 haspassages through it, such as that shown by reference 21 in FIG. 1,coming from the storage tank 2. In order to ensure that the leakagesensor proposed by the invention is sealed, the passage of any pipesrunning through the plate 101 must be sealed in turn and this can beeffected by means of a flexible bellow expansion joint 104 such as thatillustrated in FIG. 6.

The computer 32 may be provided with software which, instead of haltingthe pump 10 when the gun 51 is replaced, i.e. at the end of thedispensing operation, prolongs operation of said pump for a givenperiod, a few seconds. In this manner, if there are any leaks of liquidhydrocarbon downstream of the counter 30, a flow rate will be detectedby the computer 32 and the anomaly will be indicated to the servicestation manager. As already mentioned above, this option of detectingleaks downstream of the flow-rate counter 30 has the advantage ofhighlighting induction of liquid hydrocarbons by the vapour recoverydevices fitted to the dispensers.

What is claimed is:
 1. A leakage sensor in a dispenser for liquidhydrocarbons comprising a sealed plate arranged in a base of saiddispenser and fitted with a catchment container adapted to receive andcollect liquid hydrocarbons from hydrocarbon liquid leaks in saiddispenser, said catchment container having a level detector for saidhydrocarbons, capable of halting operation of the dispenser if thedetected level of hydrocarbons reaches a selected level.
 2. A sensor ina dispenser according to claim 1 wherein said level detector comprises afloat fitted with a position sensor.
 3. A sensor in a dispenseraccording to claim 1 wherein the dispenser contains a pump, a flow-ratecounter, and a computer, said computer being set up to detect a liquidhydrocarbon flow-rate in said counter after dispensing hydrocarbonliquid.
 4. A hydrocarbon liquid dispenser comprising: a base, a pump forpumping hydrocarbon liquid from a storage tank, and a leakage sensor fordetecting leakage of hydrocarbons in said dispenser comprising a sealedplate arranged in the base of said dispenser and fitted with a catchmentcontainer adapted to receive and collect liquid hydrocarbons, saidcatchment container having a level detector for said hydrocarbonscapable of halting operation of the dispenser if the detected level ofhydrocarbons reaches a selected level.
 5. A dispenser according to claim4 wherein said level detector comprises a float fitted with a positionsensor.
 6. A dispenser according to claim 4 further comprising aflow-rate counter and a computer, said computer being set up to detect aliquid hydrocarbon flow-rate in said counter after dispensinghydrocarbon liquid.